Re: [PATCH v11 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

On Wed, 2022-06-15 at 10:58 +0800, CK Hu wrote:

Hi, Bo-Chen:

On Fri, 2022-06-10 at 18:55 +0800, Bo-Chen Chen wrote:

...

From: Markus Schneider-Pargmann msp@baylibre.com

This patch adds a embedded displayport driver for the MediaTek mt8195 SoC.

It supports the MT8195, the embedded DisplayPort units. It offers DisplayPort 1.4 with up to 4 lanes.

The driver creates a child device for the phy. The child device will never exist without the parent being active. As they are sharing a register range, the parent passes a regmap pointer to the child so that both can work with the same register range. The phy driver sets device data that is read by the parent to get the phy device that can be used to control the phy properties.

This driver is based on an initial version by Jitao shi jitao.shi@mediatek.com

Signed-off-by: Markus Schneider-Pargmann msp@baylibre.com Signed-off-by: Guillaume Ranquet granquet@baylibre.com [Bo-Chen: Cleanup the drivers and modify comments from reviewers] Signed-off-by: Bo-Chen Chen rex-bc.chen@mediatek.com

---

[snip]

...

+static int mtk_dp_train_flow(struct mtk_dp *mtk_dp, u8 target_link_rate,

• 	     u8 target_lane_count)
  

+{

• u8 lane_adjust[2] = {};
• bool pass_tps1 = false;
• bool pass_tps2_3 = false;
• int train_retries;
• int status_control;
• int iteration_count;
• int ret;
• u8 prev_lane_adjust;
• drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LINK_BW_SET,

target_link_rate);

• drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LANE_COUNT_SET,

• 	   target_lane_count |
  

DP_LANE_COUNT_ENHANCED_FRAME_EN);

• if (mtk_dp->train_info.sink_ssc)

• drm_dp_dpcd_writeb(&mtk_dp->aux, DP_DOWNSPREAD_CTRL,
  

• 		   DP_SPREAD_AMP_0_5);
  

• train_retries = 0;
• status_control = 0;
• iteration_count = 1;
• prev_lane_adjust = 0xFF;
• mtk_dp_set_lanes(mtk_dp, target_lane_count / 2);
• ret = mtk_dp_phy_configure(mtk_dp, target_link_rate,

target_lane_count);

• if (ret)

• return -EINVAL;
  

• dev_dbg(mtk_dp->dev,

• "Link train target_link_rate = 0x%x, target_lane_count
  

= 0x%x\n",

• target_link_rate, target_lane_count);
  

• do {

• train_retries++;
  

• if (!mtk_dp->train_info.cable_plugged_in ||
  

•     mtk_dp->train_info.irq_sta.hpd_disconnect) {
  

In mtk_dp_hpd_isr_handler(), train_info.irq_sta.hpd_disconnect would finally be set to false, so you need not to check it here. So remove it here.

Hello CK,

ok, I will drop this.

...

• 	return -ENODEV;
  

• }
  

• if (mtk_dp->train_state < MTK_DP_TRAIN_STATE_TRAINING)
  

• 	return -EAGAIN;
  

• if (!pass_tps1) {
  

• 	ret = mtk_dp_train_tps_1(mtk_dp,
  

target_lane_count,

• 				 &iteration_count,
  

lane_adjust,

• 				 &status_control,
  

• 				 &prev_lane_adjust);
  

• 	if (!ret) {
  

• 		pass_tps1 = true;
  

• 		train_retries = 0;
  

• 	} else if (ret == -EINVAL) {
  

• 		break;
  

• 	}
  

• } else {
  

• 	ret = mtk_dp_train_tps_2_3(mtk_dp,
  

target_link_rate,

• 				   target_lane_count,
  

• 				   &iteration_count,
  

• 				   lane_adjust,
  

&status_control,

• 				   &prev_lane_adjust);
  

• 	if (!ret) {
  

• 		pass_tps2_3 = true;
  

• 		break;
  

• 	} else if (ret == -EINVAL) {
  

• 		break;
  

• 	}
  

• }
  

• drm_dp_dpcd_read(&mtk_dp->aux,
  

DP_ADJUST_REQUEST_LANE0_1,

• 		 lane_adjust, sizeof(lane_adjust));
  

• mtk_dp_train_update_swing_pre(mtk_dp,
  

target_lane_count,

• 			      lane_adjust);
  

• } while (train_retries < MTK_DP_TRAIN_RETRY_LIMIT &&

•  iteration_count < MTK_DP_TRAIN_MAX_ITERATIONS);
  

• drm_dp_dpcd_writeb(&mtk_dp->aux, DP_TRAINING_PATTERN_SET,

• 	   DP_TRAINING_PATTERN_DISABLE);
  

• ret = mtk_dp_train_set_pattern(mtk_dp, 0);
• if (ret)

• return -EINVAL;
  

• if (!pass_tps2_3)

• return -ETIMEDOUT;
  

• mtk_dp->train_info.link_rate = target_link_rate;
• mtk_dp->train_info.lane_count = target_lane_count;
• mtk_dp_training_set_scramble(mtk_dp, true);
• drm_dp_dpcd_writeb(&mtk_dp->aux, DP_LANE_COUNT_SET,

• 	   target_lane_count |
  

• 		   DP_LANE_COUNT_ENHANCED_FRAME_EN);
  

• mtk_dp_set_enhanced_frame_mode(mtk_dp, true);
• return ret;

+}

[snip]

...

+/*

• • We need to handle HPD signal in eDP even though eDP is a always

connected

• • device. Besides connected status, there is another feature for

HPD signal -

• • HPD pulse: it presents an IRQ from sink devices to source

devices (Refer to

• • 5.1.4 of DP1.4 spec).
• */

+static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp) +{

• bool connected;
• u32 irq_status = mtk_dp_swirq_get_clear(mtk_dp) |

• 	 mtk_dp_hwirq_get_clear(mtk_dp);
  

• struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
• if (irq_status & MTK_DP_HPD_INTERRUPT)

• train_info->irq_sta.hpd_inerrupt = true;
  

• if (irq_status & MTK_DP_HPD_CONNECT)

• train_info->irq_sta.hpd_connect = true;
  

• if (irq_status & MTK_DP_HPD_DISCONNECT)

• train_info->irq_sta.hpd_disconnect = true;
  

train_info->irq_sta.hpd_connect is used only in this function, so let hpd_connect to be local variable.

ok

...

• if (!irq_status)

• return IRQ_HANDLED;
  

• connected = mtk_dp_plug_state(mtk_dp);
• if (connected || !train_info->cable_plugged_in)

• train_info->irq_sta.hpd_disconnect  = false;
  

• else if (!connected || train_info->cable_plugged_in)

• train_info->irq_sta.hpd_connect = false;
  

• if (!(train_info->irq_sta.hpd_connect ||

•      train_info->irq_sta.hpd_disconnect))
  

• return IRQ_WAKE_THREAD;
  

• if (train_info->irq_sta.hpd_connect) {

• train_info->irq_sta.hpd_connect = false;
  

• train_info->cable_plugged_in = true;
  

• } else {

• train_info->irq_sta.hpd_disconnect = false;
  

• train_info->cable_plugged_in = false;
  

• mtk_dp->train_state = MTK_DP_TRAIN_STATE_TRAINING;
  

• }
• train_info->cable_state_change = true;
• return IRQ_WAKE_THREAD;

+}

[snip]

...

+static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,

• 		   struct drm_dp_aux_msg *msg)
  

+{

• struct mtk_dp *mtk_dp;
• bool is_read;
• u8 request;
• size_t accessed_bytes = 0;
• int ret = 0;
• mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
• if (!mtk_dp->train_info.cable_plugged_in ||

•    mtk_dp->train_info.irq_sta.hpd_disconnect) {
  

In mtk_dp_hpd_isr_handler(), train_info.irq_sta.hpd_disconnect would finally be set to false, so you need not to check it here. So remove it here.

ok, I will drop this

BRs, Bo-Chen

Regards, CK

...

• ret = -EAGAIN;
  

• goto err;
  

• }
• switch (msg->request) {
• case DP_AUX_I2C_MOT:
• case DP_AUX_I2C_WRITE:
• case DP_AUX_NATIVE_WRITE:
• case DP_AUX_I2C_WRITE_STATUS_UPDATE:
• case DP_AUX_I2C_WRITE_STATUS_UPDATE | DP_AUX_I2C_MOT:

• request = msg->request &
  

~DP_AUX_I2C_WRITE_STATUS_UPDATE;

• is_read = false;
  

• break;
  

• case DP_AUX_I2C_READ:
• case DP_AUX_NATIVE_READ:
• case DP_AUX_I2C_READ | DP_AUX_I2C_MOT:

• request = msg->request;
  

• is_read = true;
  

• break;
  

• default:

• drm_err(mtk_aux->drm_dev, "invalid aux cmd = %d\n",
  

• 	msg->request);
  

• ret = -EINVAL;
  

• goto err;
  

• }
• if (msg->size == 0) {

• ret = mtk_dp_aux_do_transfer(mtk_dp, is_read, request,
  

• 			     msg->address +
  

accessed_bytes,

• 			     msg->buffer +
  

accessed_bytes, 0);

• } else {

• while (accessed_bytes < msg->size) {
  

• 	size_t to_access =
  

• 		min_t(size_t, DP_AUX_MAX_PAYLOAD_BYTES,
  

• 		      msg->size - accessed_bytes);
  

• 	ret = mtk_dp_aux_do_transfer(mtk_dp, is_read,
  

request,

• 				     msg->address +
  

accessed_bytes,

• 				     msg->buffer +
  

accessed_bytes,

• 				     to_access);
  

• 	if (ret) {
  

• 		drm_info(mtk_dp->drm_dev,
  

• 			 "Failed to do AUX transfer:
  

%d\n", ret);

• 		break;
  

• 	}
  

• 	accessed_bytes += to_access;
  

• }
  

• }

+err:

• if (ret) {

• msg->reply = DP_AUX_NATIVE_REPLY_NACK |
  

DP_AUX_I2C_REPLY_NACK;

• return ret;
  

• }
• msg->reply = DP_AUX_NATIVE_REPLY_ACK | DP_AUX_I2C_REPLY_ACK;
• return msg->size;

+}